Tuning Quantum Materials: Uniaxial Stressed Sr₂RuO₄ as an Example

You-Sheng Li^1*, Markus Garst², Jörg Schmalian², Sayak Ghosh³, Naoki Kikugawa⁴, Dmitry A. Sokolov¹, Clifford W. Hicks^1,5, Fabian Jerzembeck¹, Matthias S. Ikeda⁶, Zhenhai Hu¹, B. J. Ramshaw³, Andreas W. Rost⁷, Michael Nicklas¹, Andrew P. Mackenzie^1,7

¹Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
²Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, Karlsruhe, Germany
³Laboratory of Atomic and Solid State Physics, Cornell University, NY, USA
⁴National Institute for Materials Science, Tsukuba, Japan
⁵School of Physics and Astronomy, University of Birmingham, Birmingham, UK
⁶Department of Applied Physics, Stanford University, California, USA
⁷School of Physics and Astronomy, University of St Andrews, St Andrews, UK

* Presenter:You-Sheng Li, email:You-Sheng.Li@cpfs.mpg.de

Many unconventional superconductors show a similar phase diagram with different ground states, which can be tuned by external parameters, such as chemical doping or pressure. Recently, uniaxial stress, a directional probe, has shown the capabilities of tuning the electronic structures of Sr₂RuO₄ across a Van Hove singularity (VHS) [1, 2]. In this talk I will take Sr₂RuO₄ as an example to demonstrate versatility of the uniaxial stress technique. I will present thermodynamic probes I have been developed and discuss our main findings [3, 4]. In short, the phase diagram of Sr₂RuO₄, remaining unknown for more than two decades, has a SC dome in proximity to a magnetic phase like many unconventional superconductors. In addition, a strong reversal of the ECE around the VHS upon entering the SC state is observed. Together with theoretical calculations, these results strongly suggest a node-less gap opening at the VHS and, thus, place a strong constraint on possible SC order parameters.
[1] A. Steppke et al. Science 355, eaaf9398 (2017).
[2] V. Sunko et al. npj Quant. Mat. 4, 2397–4648 (2019).
[3] Y.-S. Li et al. Nature 607, 276–280 (2022).
[4] Y.-S. Li et al. Proc. Natl. Acad. Sci. USA 118, e2020492118 (2021).

Keywords: Unconventional superconductor, Strongly correlated system, Low temperature physics